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Theseus' Ship Paradox

If a thing has all of its parts replaced, is it still the same thing anymore?

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Page Type:Trope

Say you have an object that is sufficiently important, even if only for its sentimental value, that simply throwing it away when it wears out isn't an option. Instead, it gets replaced in piecemeal fashion: old and rotting timbers get replaced, rips and tears get patched, missing limbs and organs get prosthetics. As this process repeats, the thing in question is made up less and less of its original parts and more and more of replacements to the point that, one day, you simply aren't going to have anything of the original left. The question is, once this happens, is it still the original object or not?

More properly known as the "Ship of Theseus" or "Grandfather's Axe" paradox, this trope presents a classic philosophical conundrum. While it's often played for comedy, as common wisdom would suggest that, no, it's not still the same axe once its head and handle have both been replaced (though its owner will stubbornly insist to the contrary), sometimes it has more dramatic implications: if a person has his brain gradually replaced with electronics, for example, at what point do we cease to have a human with bits of machine in their brain and start to have a machine with bits of human in its brain? Do we ever? This scenario can also get thorny if someone rebuilds the thing in question from the discarded parts: if you have both a "new" thing made from the original material and an "original" thing made from new material, which one, if either, is the "real" one?

Examples

Film (Animated)

In WALL•E, it's implied that the titular robot had at one point or another replaced every part of his body from one of the robot spares he keeps in his house, except his motherboard. So, by the end, when Eve replaces his motherboard after it gets severely damaged, Wall-E acts like any other garbage disposal robot until Eve kisses him.

Film (Live-Action)

The Beast in The World's End. It's had every meaningful part replaced, but looks the same and runs about as junkily as it did in the '90s.

Questioned in The Last King. The narrator wonders if, after replacing each and every part of his grandfather's axe, it is still the same axe.

An early example is the Tin Woodman from The Wonderful Wizard of Oz. He pissed off a witch who enchanted his ax so that it would cut off pieces of him, and he went to a tinsmith to replace the missing parts. Eventually he was made entirely out of tin - but since it was a gradual process, he's still human Nick Chopper and not a new person.

Brought up several times, generally in regards to a Dwarfish axe which has been passed down through the family for generations: sometimes the head needed replacing, other times the shaft, still more times the eye or the bit, but it's still the same ancestral axe.

Played to the hilt in the book's climax, where no one's terribly upset that the conspiracy to influence the Dwarfish succession involved destroying the Scone of Stone and replacing it with a perfect replica: the Scone had already been replaced many times over the centuries, but it had always remained "the thing and the whole of the thing."

The Belgariad. Alluded to in the Malloreon series. Poledra tells Beldin that she's surprised he hasn't changed his tunic during the thousands of years since she last saw him. Beldin says that he patches it, and replaces the patches as they wear out, to the point that the original tunic "is only a memory".

Honor Harrington mentions that a particular chair has been in the Protector's Palace nursery for over seven hundred years, plus or minus the odd frame repair or reupholstering.

Live Action TV

A popular example comes from the British sit-com Only Fools and Horses, where Trigger, one of the characters, is given a medal for owning the same broom for 20 years, although it has had 17 new heads and 14 new handles. When asked how can it be the same broom, Trigger produces a picture of himself and his broom and asks, "What more proof do you need?"

Discussed in an episode of Star Trek: Deep Space Nine. Kira's Romantic False Lead Bareil Antos gets injured and has part of his brain replaced with cybernetics. As more of his brain fails and is replaced, the less he's him. Eventually he's mostly cybernetics, and rather than continue the process Kira allows him to die.

Star Trek from the beginning has begged this question ever since it was described how the transporters work. The transporter's function on the show was to be a magic elevator that took the away team to the planet without requiring the director to film a shuttle landing over and over again. The transporters work by dissolving the away team member and assembling a copy of them on the planet below, which makes you wonder if the same consciousness is moved also. Further questions are begged when you consider that in an episode of Star Trek the Next Generation, a glitch in the transporter created a copy of William Riker who was marooned on the space station he was transported from. Yet more questions are begged when one episode features the only POV shot in the entire series of someone going through the transporter and mid stream being bitten by the Monster of the Week which suggests that the experience of being transported has no break in consciousness.

Real Life

The USS Constitution, sometimes known as 'Old Ironsides' and the oldest commissioned warship still afloat. It has been around so long and had so many parts replaced that it's open to discussion if a single one is original.

Needs a better name. I'm not really sure how much of a trope this is, though.

There was a story told at my high school. A man goes in with various medical problems, and each time comes out with a new prosthesis. Finally, his brain starts to deteriorate, and they replace that with some sort of computer (it's Twenty Minutes Into The Future). The doctor assures him that this'll be the last time he'll have to come in. He asks if that means he's perfectly healthy, but the doctor informs him that he's got no organic parts left to break down.

I do think this could be a trope if the paradox shows up in-universe, but I also agree that it needs a better name. (Uh, when I wrote this it was called "Trigger's Broom". I like the current name "Ship of Theseus")

Literature: Brought up several times in The Fifth Elephant, generally in regards to a Dwarfish axe which has been passed down through the family for generations: sometimes the head needed replacing, other times the shaft, still more times the eye or the bit, but it's still the same ancestral axe.

Early example is the Tin Woodman from The Wizard Of Oz. He pissed off a witch who enchanted his ax so that it would cut of pieces of him, and he went to a tinsmith to replace the missing parts. Eventually he was made entirely out of tin - but since it was a gradual process, he's still human Nick Chopper and not a new person.

Discussed in an episode of Star Trek Deep Space Nine. A former freedom fighter friend of Kira's gets injured and has part of his brain replaced with cybernetics. As more of his brain fails and is replaced, the less he's him. Eventually he's mostly cybernetics, and rather than continue the process Kira allows him to die.

Alluded to in the Malloreon. Poledra tells Beldin that she's surprised he hasn't changed his tunic during the thousands of years since she last saw him. Beldin says that he patches it, and replaces the patches as they wear out, to the point that the original tunic "is only a memory".

A few issues here. First off, I do think this is a trope. It's mentioned in many pieces, both in lit, tabletop and screen. If it's not specifically discussed, then it's certainly prevalent and used. Secondly, I don't agree that the US (not USS, which stands for United States Ship) Constitution is a Ship of Theseus. The original wording hasn't been changed since the date it was published and all changes are added onto the bill of rights, aka the Amendments. You're free to look in The Other Wiki and check that out.

A few more examples for you:

Under Literature, you could name the philosopher John Locke. He mentions the Ship in a humorous manner by using his sock as a metaphor: if I put a patch on my sock every time it tears, I will eventually replace the entire sock with patches. Is it still my sock?

Also, Terry Pratchett's example makes fun of a Real Life example, which is George Washington's axe. If I have his axe, but the blade was replaced 7 times and the handle 7 times, is it still his axe?

In Brandon Sanderson's book, "Alcatraz vs. The Scrivener's Bones," this trope is actually discussed by name. The narrator references it several times, before finally revealing its relevance in the final pages. Paraphrased a little:

The Tin Woodsman issue gets further confused in The Tin Woodsman of Oz where he encounters his chopped-off head ... and since there is no death in Oz, it's still alive and still thinks of itself as Nick Chopper.

^^^It was a combination of Nick Chopper's and Captain Fyter's (the Tin Soldier) bodies, named Chopfyt. Fyter also fell in love with the same girl and had the same thing happen to him. It's Fyter's head on the body; Chopper's head is kept in a cubbard.

Stanislaw Lem had several stories pondering when "transhumanism" turns into "switcheroo", naturally all at least bordering on Black Comedy. In Przekladaniec (Roly Poly, also film adaptation by Andrzej Wajda) a racing car driver can't pay for prosthetics and sued to return them... the problem is, there's nothing else left -- even his brain eventually got all replaced.

A recent Futurama episode had Hermes exchanging his Bodyparts with artificial robotic parts. Dr Zoidberg was saving the original parts and put them back together as a Ventriloquist's Dummy. The final part Hermes wanted was a robot-brain, wich Zoidberg transplanted and than by inserting the human brain in the Dummy he turned Hermes back to a human.

^^I think the Bicentennial Man counts, since it's a change from robot to living, but Bender spontaneously changes from a metal robot to a wooden one, with no real explanation as to how its done.

The description is bad. The laconic will not be seen on the page when it launches, so the body must contain a brief explanation, not just "see X". It would probably be a good place to talk about the original Ship of Theseus, and how it was replaced board by board, but is it still the same ship?

In Wall E, it's implied that the titular robot had at one point or another replaced every part of his body from one of the robot spares he keeps in his house, except his motherboard. So, by the end, when Eve replaces his motherboard after it gets severely damaged, Wall-E acts like any other garbage disposal robot until Eve kisses him.

^^^It's the USS Constitution, the actual ship. This is the 2nd time this "correction" came up, so perhaps it'd be useful to note in the example that it's explicitly referring to the ship and not the document.

There is no trope named Show Of Theseus--that's a leftover redirect to Long Runner Cast Turnover. But that was a snowclone. This is the original term, which makes it a little better, but it's still pretty obscure. (And likely to be confused with something to do with Shipping.) I've always heard it as Grandfathers Axe Paradox. But a clearer name, or at least some good redirects would be a really smart move here.

^ Education is probably better done in the description, where people can read and learn, rather than in the title, where the obscurity of the term simply means that people won't find it in the first place.

Evidence shows that obscurely-named tropes don't end up on work pages. No one will be adding this to any new work pages if they can't remember what it was called (or where they saw it). An unclear name is a strong obstacle to trope growth.

You might be able to get away with using some clear redirects, but even that is going to impede growth to some extent.

John Dies At The End: At least one version opens with the ax paradox. You kill a guy with an ax, the head breaks, you replace the head. You kill a badger-demon-thing with the ax, the handle breaks, you replace the handle. The original guy comes back as an intelligent corpse out for revenge, takes one look and yells, "That's the ax you killed me with!" Is he right?

In the Fifth Elephant example, the new dwarf king specifically compares changing a society's laws or customs (in this case, admitting that some dwarfs are females) to replacing components of your grandfather's axe. He also gives a brand-new axe to Vimes, saying that someday it will be an ax like this.

Honor Harrington mentions that a particular chair has been in the Protector's Palace nursery for over seven hundred years, plus or minus the odd frame repair or reupholstering.

The original example is a museum-piece ship once owned by the Greek hero Theseus. Over time, some of the planks rot out and you replace them, until eventually every single piece has been replaced and you start wondering if it's really Theseus's ship anymore.

A famous ontological paradox needs more of an entry than "The laconic says it all", even if it does.

Look people, it's an existing term. It doesn't matter if people don't know what it is; that would be like replacing "Mac Guffin" because people might not have heard of it. It's even in Wikipedia as "Ship of Theseus".

Just because *you* haven't heard of a term doesn't make it an obscure term. This is especially the case for terms that don't fall into Most Tropers Are Young Nerds territory--the skewed demographic of TV Tropes is often unusually likely not to know some things that have wide usage outside TV Tropes.

So on said Google Search, how many results in the first ten or so were about the paradox itself and how many were about the recent film by the same name?

It's not a good name for a trope. It's completely, 100% meaningless to anyone who doesn't already know exactly what it is. It doesn't even provide the slightest hint as to what it's about. Go to Naming A Trope. It specifically says that just because there is a preexisting term for something doesn't mean it necessarily should be used.

And I've heard Transhumanists try and use it in arguments both in favor of and against Brain Uploading. Along the lines of "your cells replace themselves every seven years, how is cutting apart your brain and copying the data to a computer different." Or conversely, "if you lose your grandfather's axe entirely and make a perfect copy down to the last dent is it the same? No, and your body is no different."

I'll say this: When I was searching for this discussion to bring it back into the light of day, I found it under "grandfather's axe" because I couldn't remember whose ship it was. And since the Wikipedia article on the subject lists that as a variant name, I would be fine with it as a main title.

Ideally, a title should give the reader an idea of its meaning without having to read the page. Since this is such an abstract concept, there's no title that can be comprehensible on its own. Therefore, it makes sense to go with a preexisting term that the largest number of people will recognise.

But regardless, it's prudent to create redirects for alternate titles so that people can more easily find them. From that, accepting that Ship Of Theseus seems to be the most accepted term for the idea, it seems reasonable to have that for the title with Grandfather's Axe as an alternate.

Also from Discworld, Granny Weatherwax's broom mentions the trope indirectly: it never starts on the first go, requiring some undignified running up and down to get it started. Baffled dwarf engineers have replaced the handle and bristles dozens of times each, to no effect.

Touched upon in one episode of Bump In The Night, where Molly loses her arm and gets a gorilla arm as a temporary replacement. She promptly goes mad with power and starts replacing her other body parts until she's a hulking monster with a doll's head attached - and she decides she wants to replace that, too, with Mr. Bumpy's head. In the meantime, Squishington reassembles Molly's discarded parts into the original Molly, who wakes up with no memory of her power trip.

How about Doctor Who as an example? Each regeneration has its own unique personality, and even though they are all the same individual in essence, physically they are not.
Also, the 9th Doctor's adventures are completely different to those of the 11th. I bet this applies to the old series as well (I bet).

In A Fire Upon The Deep and it's sequel, Children Of The Sky by Vernor Vinge, there's a race of Hive Mind aliens known as the "Tines". Resembling a pack of dogs, an individual Tine is actually composed of 3 - 5 of the individual dog creatures. Collectively, they make an individual intelligence. The identity is distinct and thinks of itself in the singular (referring to itself as "I" rather than "we") and might persist over hundreds of years, with each member of the pack being replaced with puppies as they grow old and die. Interestingly, it's noted in-story that while the personality and behavior of the individual changes over the years (reflecting turnover in pack members), the collective memory, and thus identity, persists.

The entire human skeleton is rebuilt in this fashion as a child's bones grow. New bone matrix is layered onto the outer surface of the bone, making it get larger, while the interior walls are eroded so the marrow cavities inside can expand proportionately. By the time a bone has doubled in size, all the matrix it started out with is dissolved away.

Discussed fairly often in Ghost In The Shell. As technology (and, in particular, cyborgization and soul-to-data conversion) run rampant, there are often questions along the lines of "what is self?" or "do we need a Shell to exist?" For the record, protagonist Motoko Kusanagi managed to "transcend" herself into the Internet, allowing her to exist without a body and live in a stream of data (though she still has her old cyborg body).

This trope is the basis of the Paddy's Axe (aka Grandfather's Axe) joke. Paddy is telling a friend how his axe has had three new heads and seven new handles but it's still just as good as the day he bought it.

Daniel C. Dennett's short story "Where Am I?" tells about what happens when a man loses first his body, then his brain, and is left with mechanical and electronic analogs. In this case, the answer to the trope's question is that he's not the same man ... because there winds up being two of him.

Discworld: The Fifth Elephant: The Low King of the Dwarves, Rhys Rhysson, discusses this point with Sam Vimes towards the end of the book, in a literal case of Grandfather's Axe; his ceremonial family axe, an heirloom passed down for generations, has occasionally required a new handle, or a new head. Of course, this is only brought up because the Scone of Stone itself is "false", sort of - it's been replaced every so often, but the dwarves' belief that it is the Stone of Scone makes it the Scone of Stone.

^ A YKTTW proposal automatically becomes Up For Grabs two months after the last post by its creator/OP. The OP TARDIS2468 hasn't posted here since they first created it back in 2012, so it's Up For Grabs.

John Dies At The End: The film opens with David beheading a body. However, the handle breaks and he gets the handle replaced. Later on, he chips the head killing a centipede... thing. Eventually, the guy he beheaded comes Back From The Dead, and the reanimated corpse and points to the axe and says "that's the axe that killed me," to which David says "is it?"

Real Life: Some Long Runner bands have replaced people such that a current lineup no longer has any of the original (or famous) members. For example, the current lineup of Rockapella has only one member who was on Where in the World is Carmen Sandiego?, and at that time he had just joined (replacing an original member who was part of the audition when they got the gig).

The Jules Verne story Dr. Ox's Experiment describes the Van Tricasse family where the surviving spouse always marries someone younger, thus continuing the same marriage for hundreds of years. Verne alludes to the example of replacing a knife blade and a knife handle when describing it.

This has been talked about in 9 Hours, 9 Persons, 9 Doors: The character Clover refers to it both as the Ship of Theseus and Locke's Socks, where all of the fabric in a sock was eventually replaced by other patches of fabric.

In addition, the same idea was cited in the game's sequel, Virtue's Last Reward, in reference to medical mannequins.

My brother spirited away both of those games, so I'm not able to find the exact examples at the moment.

What's wrong with the name Ship Of Thesesus? Add the word "paradox" or "conundrum" to the end if you must, but that is what this is called in the outside world. When The Other Wiki has a page on the same subject with the same title, I think it's pretty valid.

Ghost In The Shell Stand Alone Complex touches on this, indirectly, in the episode "Machines Desirantes". The Tachikomas speculate that humanity is no longer sure where the line falls between humans and machines, due to advances in cyborg augmentation.

I don't think this should be a trope as it stands. It is an interesting question, a bit of a Schroedinger's Cat situation: in this case, it's up to the individual (owner of the object or, in the case of a human whose parts are being replaced, it is up to them) to decide whether they are the same.

A tropeworthy version of this would be examples of when characters in a work do or say something to lampshade this aspect. A subtle way would be reforging a sword and then giving it a new name such as they had in Lord Of The Rings. Technically, it's still the same blade even while it's not, and it's just the individual who has declared it to be a different sword.

If there are examples of people claiming an item has been rebuilt so many times it can hardly be called the original item, then that would be tropeworthy. However, if it is merely the audience that sees something has been repaired using replacement parts, I don't think that should be a viable example. After all, what purpose does it serve to the narrative for the audience to think about whether an item is the original or something entirely different? It can only serve a purpose if the characters are thinking about this.

In neither case do any other characters question if the rebuilt character is the same after having every part replaced. They do not question In Universe if Wall-e is the same because his eye is replaced, only if his motherboard (processor/brain) is replaced.

If there's at least difference in performance when the minor change is given, it is enough to count.

That means Wall-e is still a subversion :p

Come to think of it... One thing that bugged me is that some things above doesn't mention the paradox, but they just offer their own interpretation and/or solution to the issue. I kinda think they should count here, but...

The Tin Woodman example is made explicit in The Tin Woodman of Oz, the same book in which he meets the Tin Soldier and Chopfyt (the combined Nick Chopper & Captain Fyter).

Early in the book The Woodman explains things to a newcomer, Woot

"In the Land of Oz," replied the [Tin Woodman], "no one can ever be killed. A man with a wooden leg or a tin leg is still the same man; and, as I lost parts of my meat body by degrees, I always remained the same person as in the beginning, even though in the end I was all tin and no meat."

And the Tin Soldier's story

I was in love with a beautiful Munchkin girl, who lived with a Wicked Witch. The Witch did not wish me to marry the girl, so she enchanted my sword, which began hacking me to pieces. When I lost my legs I went to the tinsmith, Ku-Klip, and he made me some tin legs. When I lost my arms, Ku-Klip made me tin arms, and when I lost my head he made me this fine one out of tin. It was the same way with my body, and finally I was all tin. But I was not unhappy, for Ku-Klip made a good job of me, having had experience in making another tin man before me."

The party finds Nick Chopper's old head in a cupboard

"I don't see what right you folks have to disturb my peace and comfort, either."

"You belong to me," the Tin Woodman declared.

"I do not!"

"You and I are one."

"We've been parted," asserted the Head. "It would be unnatural for me to have any interest in a man made of tin. Please close the door and leave me alone."

Conversely, Chopfyt doesn't know who he was made of even though he's got the Tin Soldier's original head.

"Good gracious!" exclaimed Woot. "Then this must be the man whom old Ku-Klip patched together and named Chopfyt."

The man now turned toward them, still scowling.

"Yes, that is my name," he said in a voice like a growl, "and it is absurd for you tin creatures, or for anyone else, to claim my head, or arm, or any part of me, for they are my personal property."

"You? You're a Nobody!" shouted Captain Fyter.

"You're just a mix-up," declared the Emperor.

...

"But, listen, Nimmie Amee!" said the astonished Woot; "he really is both of them, for he is made of their cast-off parts."

"Oh, you're quite wrong," declared Polychrome, laughing, for she was greatly enjoying the confusion of the others. "The tin men are still themselves, as they will tell you, and so Chopfyt must be someone else."

They looked at her bewildered, for the facts in the case were too puzzling to be grasped at once.

And in one of the The Hitchhikers Guide To The Galaxy books Marvin the Android mentions that all of his parts have been replaced multiple times, except for the diodes running down the left side of his body (the only parts that have ever hurt).

Audience Reaction version: In The Ghost Of Frankenstein Ygor wants Dr. Frankenstein to put his brain in the creature's body so they'll be together forever. But since the brain is where the personality is, once that happens the creature is no longer himself! But that doesn't keep the film series from going along as if the creature is the same one all the time. In Abbot & Costello meet Frankenstein Dracula wants Costello's brain to put in the creature in order to make him calmer (even though he's pretty calm in the first place, unlike every other classic appearance), which would essentially kill Ygor!Creature.

I heard that in Real Life some people keep at least one old part when doing an overhaul/buy something new to replace the old but install an old part into it, so that the "spirit" will transfer into the new body/host over time, and then the old part can safely discarded away when the transfer is complete (when it is safe is up to debate).

Stratovarius started out as Black Water in 1984 and changed the name in 1985. The band have no original members even if one excludes the black water time. The drummer Tuamo Lassila was the last original member and he left in 1995. Timo Kotipelto the now oldest member joined in 1994.

In Flames formed in 1990 and Jesper StrÃ¶mblad (keyboard/guitar) the last original member left in 2010. Four of the current five members joined before 1999.

Blackfoot started in 1969. In 2004 the band resurrected for the second time and in 2012 it got a completely new line-up. The band now have a total of 36 former members.

Quiet Riot disbanded in 2007 when Kevin Du Brow the last original member died. The band was resurrected with no original members in 2010.

The Misfits: The oldest member is the bassist and later vocalist Jerry Only. He actually replaced Diane DiPiazza on base after the bands first month of practice.

@DAN 004: I am guilty. I didn't read past the first example which I don't think follows the parameters. No one in the film is concerned over whether Wall E is the original or an entirely different thing. At least not until he begins to behave differently, but then that has to be marked as Justified.

On Futurama, Hermes began replacing parts of his body with robot parts, allowing Dr. Zoidberg to use the discarded body parts to build a ventriloquist's dummy. Eventually Hermes has no body left, and becomes so coldly-obsessed with his enhancements that he wants his brain replaced as well. Zoidberg performs the operation, but implants the extracted brain into his flesh-dummy, bringing the "real" organic Hermes back to life.

Raising Steam has Iron Girder, the Super Prototype of the steam engine, who remains Super because her inventor constantly upgrades her. At any given point of the book she looks completely different and by the end is unlikely to have any original parts, but still has the same soul, as is made explicit in several incidents.

It is directly stated that the player characters in Borderlands 2 are not their original selves after being digitally reconstructed bit by bit at New-U Stations (respawn points). The voice at the Hyperion respawn point says that the very first time the player character had to respawn they became a different version of themselves (she also rather ominously states that the character is no longer able to have offspring).

Hyperion suggests that you do not think about the fact that this is only a digital reconstruction of your original body, which died the first time you respawned. Do NOT think about this!

Bump In The Night episode "Farewell, 2 Arms": After losing an arm, Molly replaces it with a new, stronger arm. As she likes the feeling, she starts replacing all her body parts and starts terrorising the others. Squishington gathers up her discarded parts and puts them back together, this recreates the original, sweet Molly. The two fight over who is the better Molly until it is resolved by the little sister rejecting the new Molly for the original Molly.

In Terry Pratchett's Discworld novels, this is a running gag about Granny Weatherwax's malfunctioning broom, which needs to be moving at high speed before the magic kicks in and it can fly. We're repeatedly told that the best Dwarf engineers in the Ramtops have replaced the handle and twigs dozens of times to no avail, and confess themselves utterly flummoxed. It's never explicitly stated, but given Granny's personality and her recklessly self-centred approach to flying, it's highly possible that the problem is with her, not the broom, she just won't admit it.

Similarly, in The Fifth Elephant, it's revealed that the fabled Scone of Stone, the seat of the Low King of the Dwarves since time immemorial, is actually a cunning replica and the real one wore out years ago. At the end of the novel, King Rhys give Vimes a battleaxe, and says that it will be handed down in the Vimes family, sometimes needing a new blade, maybe even a new handle, but always the same axe that Duke Samuel was given by King Rhys to illustrate the sentimental and symbolic value the Scone has even if it's only a plaster cast of the original.

It is a widely-believed myth that the human body replaces all its cells (sometimes given as all its atoms) every seven (or ten, or whatever) years. Averted, as this is just that: a myth. The cells in the body die off and are replaced at different rates, and some, most notably the neurons in the brain, last a lifetime and are never replaced if they die prematurely.

Also, I tend to agree that this needs to be thrown to a Title Crowner, as "Ship of Theseus" is the standard term for this question among philosophical circles.

^^ Ah yes, the myth that is the rallying cry of Transhumanists all over the globe.

In the 1990s stem cells that can replace a small amount of neurons were discovered in the brains of humans and some other animals. Which some interpreted to mean that Brain Uploading could be possible. However a 2014 study found that neurogenesis causes memory loss, so the human body is not an example after all.

Wouldn't this be Useful Notes not a trope? I mean Schrodingers Cat is referenced in a ton of works too as a metaphor for something or another, but it's still explicitly a Useful Notes page. Not a trope page. I don't see how the Ship of Theseus would be treated any different since they're both thought exercises explored in fiction.

Real Life: Microsoft Windows considers the motherboard to be what makes a given computer. You can upgrade any & all other components including the CPU multiple times, but if you replace the motherboard with any but an identical model then you have a new computer and have to buy a new copy of Windows to put on it.

The steam engine Super Prototype, Iron Girder, in Raising Steam is constantly being upgraded by its inventor, at such a rate that it looks completely different every time the main character sees it. However, everyone always agrees that it's still Iron Girder, and this turns out to be because it's the avatar of the newly born goddess of steam engines.

I think there needs to be some kind of recognition— maybe a full-on Internal Subtrope— of examples which do not fit the strict requirements of a Ship of Theseus situation because there is a part or parts that IS constant. Sometimes, that part is even explicitly identified as the part that contains the "identity" of whatever-it-is, as in the Microsoft Windows example above where Windows identifies a computer by its motherboard, no matter what else is replaced.

Another example of the above type:

Anime & Manga

In One Piece, the protagonists' first Cool Boat, the Going Merry, is declared unfixable when the keel is broken. It's explicitly stated that even if every other part of the ship were salvaged and added to a new keel, it would not be the same ship.

Oh wow, I discussed this exact thing with the Classics and Philosophy professors at Oxford not long ago. Their views propose so many different variations and look at the product of locality in causing the differing opinions on Ship A, Ship B, Ship C or — my favourite — Ship 0. I suggested this one to them and Rosa (loci professor, philosophy) and they started offering it as another opinion!

Ship 0 asserts that, even looking at every point in the Ship's' past as a separate universe (at one point, Ship X was the only true one), after the entire transformation none of the remaining Ships, past and present, are the real one, but each contain a component of the idea of the Ship.

Another from Doctor Who: Per a discussion in "Day of the Doctor" the Doctor's sonic screwdriver is identical on a software level to its previous & future incarnations, even though its hardware/outer casing has changed. This is used as a Chekhovs Gun, twice.

I've actually found an example that makes serious mention of this in-universe. Actually, it may be mentioned somewhere above, but it's late and I'm tired and don't want to read.

John Dies At The End... At the beginning, he's talking about a series of events that break parts of "your" axe, first the handle, then the axe head and both need to be replaced. A zombie mentions the axe as being the same originally used to kill it, but the narrator questions if that's true.

^ I'd have it backwards, Theseus Ship is not clear. it's the proper name yes but if it requires classical knowledge, it fails. Theseus is more known as "guy who goes to a labyrinth to face A Load Of Bull".

EDIT: Both of you did say the same thing, that someone would search for the description. Why? They want to find out what it's called. Shanghai Slave, they would discover it was called Galatea, which is what they really wanted. So, the name from Classical Mythology. We already have Lotus Eater Machine, a reference that may confuse people who don't know about it enough for it to be explained. Just add a sentence at the top of the page. It also avoids the issue if the fact that it's not a paradox, it's more of a postulate or something, but that wouldn't make for a great name.

^^ Shangha Slave We are in agreement. You search for Part Replacement thingamabob in the search bar, a trope called Ship of Theseus shows up. You get aha moment of "That's what it's called' You just educated yourself.

@ Acrobox: what about "You search for Part Replacement thingamabob in the search bar, a trope called Ship of Theseus shows up." and then "you skip it because it doesn't look like what I wanted."? It is true story, mind you.

^ No, it's not. It's the standard, real-world name for the trope, used in academic and philosophical circles for literally thousands of years. We're not going out of our way to make some piece of fiction we're trying to pimp into a Trope Namer, we're using an existing term that is recognizable to those who care about such things.

That said: crowner, plz. Nobody is going to convince anybody else at this point.

Now, what about that problem where you and your friend's memories are slowly swapped. At what point, if any, do you become your friend and vice versa? A common accompanying problem to go with The Ship Of Theseus, but a more relateable one (apparently) as people nowadays prefer to think of mad scientists than ancient wooden boats being rebuilt en-route.

Same hat my ancient ancestor wore back when he was a private eye in the nineteen-fifties. Sure it's had thirty new brims, eighty new bands and more crowns than the House of Hapsburg since then, but it's the same hat. Same old hat, same old joke. Class never dates, see?

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